1. Field of the Invention
The present invention relates to an automatic speed-change apparatus for automatically changing the speed of a gear transmission.
2. Description of the Related Art
There has been provided an apparatus in which a manual gear transmission mechanism is used as it is and speed-change and clutch operations are automated through a hydraulic apparatus by computer control. This apparatus, however, requires three cylinders for clutch, shift and select operations, and a number of solenoid valves for driving these cylinders as well as a hydraulic system. Due to this, the apparatus has disadvantages in complicated structure, large size and high cost.
In addition, there has been provided an apparatus in which motors are employed to the select and change speed actuators for a gear transmission, as disclosed by, for example, Japanese Patent Publication No. 61-51697. This apparatus, however, requires as many motors as select lines and a plurality of motors and solenoid valves are used. Due to this, this apparatus has disadvantages in complicated structure, large size and high cost.